Investment casting is a commonly used technique for forming metallic components having complex geometries, especially hollow components, and is used in the fabrication of superalloy gas turbine engine components such as blades and vanes and their hollow airfoils.
Advanced airfoil designs have very thin metal walls and complex cooling passages. Depending upon the size of the features to be cast, these cooling passages are formed either with ceramic mini-cores and/or refractory metal cores. The combined features make the cooling passages extremely difficult to cast successfully due to the high surface area of ceramic in relation to the amount of metal in the thin wall areas. Ceramic to molten metal contact has a high surface tension associated with such contact. The ceramic does not ‘wet out’ easily leading to non-fill defects.
Consequently, there exists room for improvements in the investment casting process.